This invention relates to laser alignment tools, and in particular to a self-leveling laser alignment tool and method which compensates for material stiffness of a pendulum suspension system.
A variety of survey and carpentry tools have previously employed lasers to improve accuracy and reliability of leveling. To further improve the accuracy of such laser alignment tools, there are several methods to automatically self-level either the laser or a reflective surface within the laser alignment tool.
In one general category of automatic self-leveling, a pendulum suspension system is used to level the laser by gravity. In one pendulum suspension system example, the laser or reflective surface is suspended by a ball bearing pivot within a housing. However, at tilt angles close to level the force available to overcome the friction in the ball bearings is quite small, leading to inaccuracy.
In another pendulum suspension system example, the laser or reflective surface is hung by a flexible support member, such as a thread, a wire or a coil spring. Threads, however, provide little if any torsion resistance, thereby leading to line orientation difficulties. Additionally, at tilt angles, material stiffness (i.e., bending, strain, deflection) of the wire or coil spring although small, does not allow the pendulum suspension system to hang truly plumb, thereby also leading to inaccuracy.
Accordingly, there is a need for a leveling technique which compensates for material stiffness in a pendulum suspension system of a laser alignment tool.